High Pressure X-ray Diffraction Studies on Barium

Area of Science:

• Solid-state physics
• Materials science
• Crystallography

Background:

• Previous studies by Bridgman identified volume and resistance transitions in barium at different pressures.
• The precise relationship between these transitions and structural changes in barium remained unclear.

Purpose of the Study:

• To elucidate the relationship between Bridgman's observed volume and resistance transitions in barium.
• To determine the crystal structure and lattice parameters of barium under high pressure.

Main Methods:

• Simultaneous in-situ X-ray diffraction and electrical resistance measurements were performed on barium under high pressure.
• High-pressure cell and diamond anvil cell techniques were employed.

Main Results:

• The 78-kilobar (kb) resistance transition in barium was found to be identical to the 59-kb volume transition.
• During this transition, barium transforms from a body-centered cubic (BCC) structure to a hexagonal close-packed (HCP) structure.
• Precise lattice parameters and compression values were determined for the HCP phase at high pressures, showing discrepancies with previous reports.

Conclusions:

• The study definitively links the volume and resistance transitions in barium, attributing them to a single structural transformation.
• The findings provide accurate structural data for barium under pressure, refining previous measurements and understanding of its phase behavior.